The present invention relates to portable automotive lifting devices of the service jack type, such as rolling jacks, trolley jacks and double arm pivot parallelogram jacks.
Service jacks are well known, and are defined in ASME PALD-1993, Part 10, as "a self-contained device designed for lifting, but not sustaining, a partial vehicular load, consisting of a frame with wheels and/or swivel casters supporting a mechanism that actuates a pivoting lift arm equipped with a saddle." Conventional service jacks are not entirely satisfactory in that they commonly exhibit one or more of the following disadvantages:
1. When the service jack is rolled under the body of a vehicle, the lift arm saddle, which engages the vehicle at the lift or jacking point (hereinafter, the "lift point") so as to raise the vehicle is partially or entirely obscured from the view of the operator. PA1 2. The operator, when in a standing position, cannot see the lift point on the underside of the vehicle so as to properly locate the saddle for engagement with the lift point. PA1 3. Modern vehicles have tightly defined lift points located on the frame, the unibody joints, the subframe and/or suspension parts. Attempting to raise the vehicle at the wrong point may result in damage to underside areas of the vehicle which are not structurally designed to function as lift points. PA1 4. In order to align the jack with a lift point of the vehicle, the operator must get down in a hands and knees position to look under the body of the vehicle to manipulate the typically heavy service jack into the proper position. PA1 5. In the hands and knees position, the view of the underside of the vehicle is from the side, instead of from below looking up at the vehicle underside so as to be able to positively locate the lift point. PA1 6. If the service jack is located under the vehicle without the proper visual alignment, the saddle may either (a) lift against a part of the vehicle not designed to carry the weight of the vehicle, thereby damaging the vehicle or (b) be seated on an angled or slippery component of the vehicle, which may result in the vehicle suddenly sliding off of the jack, thereby creating a safety hazard.
Thus there is a need for an improvement in the conventional service jack to enable the operator to indirectly view the underside of a vehicle from a standing position while positioning the saddle so as to avoid these disadvantages of the prior art service jacks.